diff --git a/ci/test/02_run_container.py b/ci/test/02_run_container.py
index 4d0bed2ad41..311fe923954 100755
--- a/ci/test/02_run_container.py
+++ b/ci/test/02_run_container.py
@@ -26,7 +26,6 @@ def main():
         ["bash", "-c", "grep export ./ci/test/00_setup_env*.sh"],
         stdout=subprocess.PIPE,
         text=True,
-        encoding="utf8",
     ).stdout.splitlines()
     settings = set(l.split("=")[0].split("export ")[1] for l in settings)
     # Add "hidden" settings, which are never exported, manually. Otherwise,
@@ -42,7 +41,7 @@ def main():
         u=os.environ["USER"],
         c=os.environ["CONTAINER_NAME"],
     )
-    with open(env_file, "w", encoding="utf8") as file:
+    with open(env_file, "w") as file:
         for k, v in os.environ.items():
             if k in settings:
                 file.write(f"{k}={v}\n")
diff --git a/contrib/devtools/circular-dependencies.py b/contrib/devtools/circular-dependencies.py
index b742a8cea67..09362c9f41e 100755
--- a/contrib/devtools/circular-dependencies.py
+++ b/contrib/devtools/circular-dependencies.py
@@ -49,7 +49,7 @@ for arg in sys.argv[1:]:
 # TODO: implement support for multiple include directories
 for arg in sorted(files.keys()):
     module = files[arg]
-    with open(arg, 'r', encoding="utf8") as f:
+    with open(arg, 'r') as f:
         for line in f:
             match = RE.match(line)
             if match:
diff --git a/contrib/devtools/clang-format-diff.py b/contrib/devtools/clang-format-diff.py
index 30e804dbe27..f3515631738 100755
--- a/contrib/devtools/clang-format-diff.py
+++ b/contrib/devtools/clang-format-diff.py
@@ -169,7 +169,7 @@ def main():
             sys.exit(p.returncode)
 
         if not args.i:
-            with open(filename, encoding="utf8") as f:
+            with open(filename) as f:
                 code = f.readlines()
             formatted_code = StringIO(stdout).readlines()
             diff = difflib.unified_diff(
diff --git a/contrib/devtools/copyright_header.py b/contrib/devtools/copyright_header.py
index 12d7276455c..39b67ec4929 100755
--- a/contrib/devtools/copyright_header.py
+++ b/contrib/devtools/copyright_header.py
@@ -140,7 +140,7 @@ def file_has_without_c_style_copyright_for_holder(contents, holder_name):
 ################################################################################
 
 def read_file(filename):
-    return open(filename, 'r', encoding="utf8").read()
+    return open(filename, 'r').read()
 
 def gather_file_info(filename):
     info = {}
@@ -316,12 +316,12 @@ def get_most_recent_git_change_year(filename):
 ################################################################################
 
 def read_file_lines(filename):
-    with open(filename, 'r', encoding="utf8") as f:
+    with open(filename, 'r') as f:
         file_lines = f.readlines()
     return file_lines
 
 def write_file_lines(filename, file_lines):
-    with open(filename, 'w', encoding="utf8") as f:
+    with open(filename, 'w') as f:
         f.write(''.join(file_lines))
 
 ################################################################################
diff --git a/contrib/filter-lcov.py b/contrib/filter-lcov.py
index db780ad53bd..373dfe3ee67 100755
--- a/contrib/filter-lcov.py
+++ b/contrib/filter-lcov.py
@@ -16,8 +16,8 @@ pattern = args.pattern
 outfile = args.outfile
 
 in_remove = False
-with open(tracefile, 'r', encoding="utf8") as f:
-    with open(outfile, 'w', encoding="utf8") as wf:
+with open(tracefile, 'r') as f:
+    with open(outfile, 'w') as wf:
         for line in f:
             for p in pattern:
                 if line.startswith("SF:") and p in line:
diff --git a/contrib/linearize/linearize-data.py b/contrib/linearize/linearize-data.py
index 74d98307056..1613f5cae23 100755
--- a/contrib/linearize/linearize-data.py
+++ b/contrib/linearize/linearize-data.py
@@ -34,7 +34,7 @@ def get_blk_dt(blk_hdr):
 # When getting the list of block hashes, undo any byte reversals.
 def get_block_hashes(settings):
     blkindex = []
-    with open(settings['hashlist'], "r", encoding="utf8") as f:
+    with open(settings['hashlist'], "r") as f:
         for line in f:
             line = line.rstrip()
             if settings['rev_hash_bytes'] == 'true':
@@ -267,7 +267,7 @@ if __name__ == '__main__':
         print("Usage: linearize-data.py CONFIG-FILE")
         sys.exit(1)
 
-    with open(sys.argv[1], encoding="utf8") as f:
+    with open(sys.argv[1]) as f:
         for line in f:
             # skip comment lines
             m = re.search(r'^\s*#', line)
diff --git a/contrib/linearize/linearize-hashes.py b/contrib/linearize/linearize-hashes.py
index 695bafad342..ddd9a7ba23b 100755
--- a/contrib/linearize/linearize-hashes.py
+++ b/contrib/linearize/linearize-hashes.py
@@ -87,7 +87,7 @@ def get_block_hashes(settings, max_blocks_per_call=10000):
 
 def get_rpc_cookie():
     # Open the cookie file
-    with open(os.path.join(os.path.expanduser(settings['datadir']), '.cookie'), 'r', encoding="ascii") as f:
+    with open(os.path.join(os.path.expanduser(settings['datadir']), '.cookie'), 'r') as f:
         combined = f.readline()
         combined_split = combined.split(":")
         settings['rpcuser'] = combined_split[0]
@@ -98,7 +98,7 @@ if __name__ == '__main__':
         print("Usage: linearize-hashes.py CONFIG-FILE")
         sys.exit(1)
 
-    with open(sys.argv[1], encoding="utf8") as f:
+    with open(sys.argv[1]) as f:
         for line in f:
             # skip comment lines
             m = re.search(r'^\s*#', line)
diff --git a/contrib/message-capture/message-capture-parser.py b/contrib/message-capture/message-capture-parser.py
index 0f409717d4c..19ab8d02c7a 100755
--- a/contrib/message-capture/message-capture-parser.py
+++ b/contrib/message-capture/message-capture-parser.py
@@ -205,7 +205,7 @@ def main():
 
     jsonrep = json.dumps(messages)
     if output:
-        with open(str(output), 'w+', encoding="utf8") as f_out:
+        with open(str(output), 'w+') as f_out:
             f_out.write(jsonrep)
     else:
         print(jsonrep)
diff --git a/contrib/seeds/generate-seeds.py b/contrib/seeds/generate-seeds.py
index a3ce0122519..41261091c4d 100755
--- a/contrib/seeds/generate-seeds.py
+++ b/contrib/seeds/generate-seeds.py
@@ -168,16 +168,16 @@ def main():
     g.write(' *\n')
     g.write(' * Each line contains a BIP155 serialized (networkID, addr, port) tuple.\n')
     g.write(' */\n')
-    with open(os.path.join(indir,'nodes_main.txt'), 'r', encoding="utf8") as f:
+    with open(os.path.join(indir,'nodes_main.txt'), 'r') as f:
         process_nodes(g, f, 'chainparams_seed_main')
     g.write('\n')
-    with open(os.path.join(indir,'nodes_signet.txt'), 'r', encoding="utf8") as f:
+    with open(os.path.join(indir,'nodes_signet.txt'), 'r') as f:
         process_nodes(g, f, 'chainparams_seed_signet')
     g.write('\n')
-    with open(os.path.join(indir,'nodes_test.txt'), 'r', encoding="utf8") as f:
+    with open(os.path.join(indir,'nodes_test.txt'), 'r') as f:
         process_nodes(g, f, 'chainparams_seed_test')
     g.write('\n')
-    with open(os.path.join(indir,'nodes_testnet4.txt'), 'r', encoding="utf8") as f:
+    with open(os.path.join(indir,'nodes_testnet4.txt'), 'r') as f:
         process_nodes(g, f, 'chainparams_seed_testnet4')
     g.write('#endif // BITCOIN_CHAINPARAMSSEEDS_H\n')
 
diff --git a/contrib/seeds/makeseeds.py b/contrib/seeds/makeseeds.py
index 0e5826ef875..1cb9603998a 100755
--- a/contrib/seeds/makeseeds.py
+++ b/contrib/seeds/makeseeds.py
@@ -211,7 +211,7 @@ def main():
     print('Done.', file=sys.stderr)
 
     print('Loading and parsing DNS seeds…', end='', file=sys.stderr, flush=True)
-    with open(args.seeds, 'r', encoding='utf8') as f:
+    with open(args.seeds, 'r') as f:
         lines = f.readlines()
     ips = [parseline(line) for line in lines]
     random.shuffle(ips)
diff --git a/contrib/verify-binaries/verify.py b/contrib/verify-binaries/verify.py
index 6c07b36c9d8..6f5a933ffff 100755
--- a/contrib/verify-binaries/verify.py
+++ b/contrib/verify-binaries/verify.py
@@ -246,8 +246,8 @@ def files_are_equal(filename1, filename2):
     eq = contents1 == contents2
 
     if not eq:
-        with open(filename1, 'r', encoding='utf-8') as f1, \
-                open(filename2, 'r', encoding='utf-8') as f2:
+        with open(filename1, 'r') as f1, \
+                open(filename2, 'r') as f2:
             f1lines = f1.readlines()
             f2lines = f2.readlines()
 
@@ -426,7 +426,7 @@ def verify_shasums_signature(
 def parse_sums_file(sums_file_path: str, filename_filter: list[str]) -> list[list[str]]:
     # extract hashes/filenames of binaries to verify from hash file;
     # each line has the following format: "<hash> <binary_filename>"
-    with open(sums_file_path, 'r', encoding='utf8') as hash_file:
+    with open(sums_file_path, 'r') as hash_file:
         return [line.split()[:2] for line in hash_file if len(filename_filter) == 0 or any(f in line for f in filename_filter)]
 
 
diff --git a/contrib/verify-commits/verify-commits.py b/contrib/verify-commits/verify-commits.py
index a1fe78a6436..808f26ed185 100755
--- a/contrib/verify-commits/verify-commits.py
+++ b/contrib/verify-commits/verify-commits.py
@@ -82,17 +82,17 @@ def main():
     # get directory of this program and read data files
     dirname = os.path.dirname(os.path.abspath(__file__))
     print("Using verify-commits data from " + dirname)
-    with open(dirname + "/trusted-git-root", "r", encoding="utf8") as f:
+    with open(dirname + "/trusted-git-root", "r") as f:
         verified_root = f.read().splitlines()[0]
-    with open(dirname + "/trusted-sha512-root-commit", "r", encoding="utf8") as f:
+    with open(dirname + "/trusted-sha512-root-commit", "r") as f:
         verified_sha512_root = f.read().splitlines()[0]
-    with open(dirname + "/allow-revsig-commits", "r", encoding="utf8") as f:
+    with open(dirname + "/allow-revsig-commits", "r") as f:
         revsig_allowed = f.read().splitlines()
-    with open(dirname + "/allow-unclean-merge-commits", "r", encoding="utf8") as f:
+    with open(dirname + "/allow-unclean-merge-commits", "r") as f:
         unclean_merge_allowed = f.read().splitlines()
-    with open(dirname + "/allow-incorrect-sha512-commits", "r", encoding="utf8") as f:
+    with open(dirname + "/allow-incorrect-sha512-commits", "r") as f:
         incorrect_sha512_allowed = f.read().splitlines()
-    with open(dirname + "/trusted-keys", "r", encoding="utf8") as f:
+    with open(dirname + "/trusted-keys", "r") as f:
         trusted_keys = f.read().splitlines()
 
     # Set commit and variables
diff --git a/test/functional/combine_logs.py b/test/functional/combine_logs.py
index 998cb208310..c4e4673228b 100755
--- a/test/functional/combine_logs.py
+++ b/test/functional/combine_logs.py
@@ -148,7 +148,7 @@ def get_log_events(source, logfile):
     Log events may be split over multiple lines. We use the timestamp
     regex match as the marker for a new log event."""
     try:
-        with open(logfile, 'r', encoding='utf-8') as infile:
+        with open(logfile, 'r') as infile:
             event = ''
             timestamp = ''
             for line in infile:
diff --git a/test/functional/feature_asmap.py b/test/functional/feature_asmap.py
index eef599f1456..139725bbba4 100755
--- a/test/functional/feature_asmap.py
+++ b/test/functional/feature_asmap.py
@@ -97,7 +97,7 @@ class AsmapTest(BitcoinTestFramework):
         self.log.info('Test bitcoind -asmap with empty map file')
         self.stop_node(0)
         empty_asmap = os.path.join(self.datadir, "ip_asn.map")
-        with open(empty_asmap, "w", encoding="utf-8") as f:
+        with open(empty_asmap, "w") as f:
             f.write("")
         msg = f"Error: Could not parse asmap file \"{empty_asmap}\""
         self.node.assert_start_raises_init_error(extra_args=[f'-asmap={empty_asmap}'], expected_msg=msg)
diff --git a/test/functional/feature_config_args.py b/test/functional/feature_config_args.py
index 441c21f03a3..14a5115ae77 100755
--- a/test/functional/feature_config_args.py
+++ b/test/functional/feature_config_args.py
@@ -55,7 +55,7 @@ class ConfArgsTest(BitcoinTestFramework):
         os.rename(conf_path.with_suffix('.confbkp'), conf_path)
 
         self.log.debug('Verifying includeconf directive pointing to directory is caught')
-        with open(conf_path, 'a', encoding='utf-8') as conf:
+        with open(conf_path, 'a') as conf:
             conf.write(f'includeconf={self.nodes[0].datadir_path}\n')
         self.nodes[0].assert_start_raises_init_error(
             extra_args=['-regtest'],
@@ -68,12 +68,12 @@ class ConfArgsTest(BitcoinTestFramework):
         self.log.info('Disabling configuration via -noconf')
 
         conf_path = self.nodes[0].datadir_path / 'bitcoin.conf'
-        with open(conf_path, encoding='utf-8') as conf:
+        with open(conf_path) as conf:
             settings = [f'-{line.rstrip()}' for line in conf if len(line) > 1 and line[0] != '[']
         os.rename(conf_path, conf_path.with_suffix('.confbkp'))
 
         self.log.debug('Verifying garbage in config can be detected')
-        with open(conf_path, 'a', encoding='utf-8') as conf:
+        with open(conf_path, 'a') as conf:
             conf.write('garbage\n')
         self.nodes[0].assert_start_raises_init_error(
             extra_args=['-regtest'],
@@ -107,9 +107,9 @@ class ConfArgsTest(BitcoinTestFramework):
             expected_msg=conf_in_config_file_err,
         )
         inc_conf_file_path = self.nodes[0].datadir_path / 'include.conf'
-        with open(self.nodes[0].datadir_path / 'bitcoin.conf', 'a', encoding='utf-8') as conf:
+        with open(self.nodes[0].datadir_path / 'bitcoin.conf', 'a') as conf:
             conf.write(f'includeconf={inc_conf_file_path}\n')
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('conf=some.conf\n')
         self.nodes[0].assert_start_raises_init_error(
             expected_msg=conf_in_config_file_err,
@@ -119,65 +119,65 @@ class ConfArgsTest(BitcoinTestFramework):
             expected_msg='Error: Error parsing command line arguments: Invalid parameter -dash_cli=1',
             extra_args=['-dash_cli=1'],
         )
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('dash_conf=1\n')
 
         with self.nodes[0].assert_debug_log(expected_msgs=['Ignoring unknown configuration value dash_conf']):
             self.start_node(0)
         self.stop_node(0)
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('reindex=1\n')
 
         with self.nodes[0].assert_debug_log(expected_msgs=['Warning: reindex=1 is set in the configuration file, which will significantly slow down startup. Consider removing or commenting out this option for better performance, unless there is currently a condition which makes rebuilding the indexes necessary']):
             self.start_node(0)
         self.stop_node(0)
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('-dash=1\n')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error: Error reading configuration file: parse error on line 1: -dash=1, options in configuration file must be specified without leading -')
 
         if self.is_wallet_compiled():
-            with open(inc_conf_file_path, 'w', encoding='utf8') as conf:
+            with open(inc_conf_file_path, 'w') as conf:
                 conf.write("wallet=foo\n")
             self.nodes[0].assert_start_raises_init_error(expected_msg=f'Error: Config setting for -wallet only applied on {self.chain} network when in [{self.chain}] section.')
 
         main_conf_file_path = self.nodes[0].datadir_path / "bitcoin_main.conf"
         util.write_config(main_conf_file_path, n=0, chain='', extra_config=f'includeconf={inc_conf_file_path}\n')
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('acceptnonstdtxn=1\n')
         self.nodes[0].assert_start_raises_init_error(extra_args=[f"-conf={main_conf_file_path}", "-allowignoredconf"], expected_msg='Error: acceptnonstdtxn is not currently supported for main chain')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('nono\n')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error: Error reading configuration file: parse error on line 1: nono, if you intended to specify a negated option, use nono=1 instead')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('server=1\nrpcuser=someuser\nrpcpassword=some#pass')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error: Error reading configuration file: parse error on line 3, using # in rpcpassword can be ambiguous and should be avoided')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('server=1\nrpcuser=someuser\nmain.rpcpassword=some#pass')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error: Error reading configuration file: parse error on line 3, using # in rpcpassword can be ambiguous and should be avoided')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('server=1\nrpcuser=someuser\n[main]\nrpcpassword=some#pass')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error: Error reading configuration file: parse error on line 4, using # in rpcpassword can be ambiguous and should be avoided')
 
         inc_conf_file2_path = self.nodes[0].datadir_path / 'include2.conf'
-        with open(self.nodes[0].datadir_path / 'bitcoin.conf', 'a', encoding='utf-8') as conf:
+        with open(self.nodes[0].datadir_path / 'bitcoin.conf', 'a') as conf:
             conf.write(f'includeconf={inc_conf_file2_path}\n')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('testnot.datadir=1\n')
-        with open(inc_conf_file2_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file2_path, 'w') as conf:
             conf.write('[testnet]\n')
         self.restart_node(0)
         self.nodes[0].stop_node(expected_stderr=f'Warning: {inc_conf_file_path}:1 Section [testnot] is not recognized.{os.linesep}{inc_conf_file2_path}:1 Section [testnet] is not recognized.')
 
-        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file_path, 'w') as conf:
             conf.write('')  # clear
-        with open(inc_conf_file2_path, 'w', encoding='utf-8') as conf:
+        with open(inc_conf_file2_path, 'w') as conf:
             conf.write('')  # clear
 
     def test_config_file_log(self):
@@ -522,9 +522,9 @@ class ConfArgsTest(BitcoinTestFramework):
         conf_file = default_data_dir / "bitcoin.conf"
 
         # datadir needs to be set before [chain] section
-        with open(conf_file, encoding='utf8') as f:
+        with open(conf_file) as f:
             conf_file_contents = f.read()
-        with open(conf_file, 'w', encoding='utf8') as f:
+        with open(conf_file, 'w') as f:
             f.write(f"datadir={new_data_dir}\n")
             f.write(conf_file_contents)
 
diff --git a/test/functional/feature_includeconf.py b/test/functional/feature_includeconf.py
index ee484e7ec50..a416b2293dd 100755
--- a/test/functional/feature_includeconf.py
+++ b/test/functional/feature_includeconf.py
@@ -24,12 +24,12 @@ class IncludeConfTest(BitcoinTestFramework):
     def run_test(self):
         # Create additional config files
         # - tmpdir/node0/relative.conf
-        with open(self.nodes[0].datadir_path / "relative.conf", "w", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "relative.conf", "w") as f:
             f.write("uacomment=relative\n")
         # - tmpdir/node0/relative2.conf
-        with open(self.nodes[0].datadir_path / "relative2.conf", "w", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "relative2.conf", "w") as f:
             f.write("uacomment=relative2\n")
-        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a") as f:
             f.write("uacomment=main\nincludeconf=relative.conf\n")
         self.restart_node(0)
 
@@ -50,7 +50,7 @@ class IncludeConfTest(BitcoinTestFramework):
         )
 
         self.log.info("-includeconf cannot be used recursively. subversion should end with 'main; relative)/'")
-        with open(self.nodes[0].datadir_path / "relative.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "relative.conf", "a") as f:
             f.write("includeconf=relative2.conf\n")
         self.start_node(0)
 
@@ -61,7 +61,7 @@ class IncludeConfTest(BitcoinTestFramework):
         self.log.info("-includeconf cannot contain invalid arg")
 
         # Commented out as long as we ignore invalid arguments in configuration files
-        #with open(self.nodes[0].datadir_path / "relative.conf", "w", encoding="utf8") as f:
+        #with open(self.nodes[0].datadir_path / "relative.conf", "w") as f:
         #    f.write("foo=bar\n")
         #self.nodes[0].assert_start_raises_init_error(expected_msg="Error: Error reading configuration file: Invalid configuration value foo")
 
@@ -70,11 +70,11 @@ class IncludeConfTest(BitcoinTestFramework):
         self.nodes[0].assert_start_raises_init_error(expected_msg="Error: Error reading configuration file: Failed to include configuration file relative.conf")
 
         self.log.info("multiple -includeconf args can be used from the base config file. subversion should end with 'main; relative; relative2)/'")
-        with open(self.nodes[0].datadir_path / "relative.conf", "w", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "relative.conf", "w") as f:
             # Restore initial file contents
             f.write("uacomment=relative\n")
 
-        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a") as f:
             f.write("includeconf=relative2.conf\n")
 
         self.start_node(0)
diff --git a/test/functional/feature_loadblock.py b/test/functional/feature_loadblock.py
index 0e6ec14c773..2bf700d16c5 100755
--- a/test/functional/feature_loadblock.py
+++ b/test/functional/feature_loadblock.py
@@ -41,10 +41,10 @@ class LoadblockTest(BitcoinTestFramework):
         hash_list = tempfile.NamedTemporaryFile(dir=data_dir,
                                                 mode='w',
                                                 delete=False,
-                                                encoding="utf-8")
+        )
 
         self.log.info("Create linearization config file")
-        with open(cfg_file, "a", encoding="utf-8") as cfg:
+        with open(cfg_file, "a") as cfg:
             cfg.write(f"datadir={data_dir}\n")
             cfg.write(f"rpcuser={node_url.username}\n")
             cfg.write(f"rpcpassword={node_url.password}\n")
diff --git a/test/functional/feature_notifications.py b/test/functional/feature_notifications.py
index 519d80b9abf..12bc6b1804e 100755
--- a/test/functional/feature_notifications.py
+++ b/test/functional/feature_notifications.py
@@ -200,7 +200,7 @@ class NotificationsTest(BitcoinTestFramework):
         self.wait_until(lambda: os.path.isfile(self.shutdownnotify_file), timeout=10)
 
     def large_work_invalid_chain_warning_in_alert_file(self):
-        with open(self.alertnotify_file, 'r', encoding='utf8') as f:
+        with open(self.alertnotify_file, 'r') as f:
             alert_text = f.read()
         return LARGE_WORK_INVALID_CHAIN_WARNING in alert_text
 
@@ -213,7 +213,7 @@ class NotificationsTest(BitcoinTestFramework):
             fname = os.path.join(self.walletnotify_dir, notify_outputname(self.wallet, tx_id))
             # Wait for the cached writes to hit storage
             self.wait_until(lambda: os.path.getsize(fname) > 0, timeout=10)
-            with open(fname, 'rt', encoding='utf-8') as f:
+            with open(fname, 'rt') as f:
                 text = f.read()
                 # Universal newline ensures '\n' on 'nt'
                 assert_equal(text[-1], '\n')
diff --git a/test/functional/feature_startupnotify.py b/test/functional/feature_startupnotify.py
index 1e071037254..d9c2f864c7d 100755
--- a/test/functional/feature_startupnotify.py
+++ b/test/functional/feature_startupnotify.py
@@ -27,7 +27,7 @@ class StartupNotifyTest(BitcoinTestFramework):
         self.log.info("Test -startupnotify is executed once")
 
         def get_count():
-            with open(tmpdir_file, "r", encoding="utf8") as f:
+            with open(tmpdir_file, "r") as f:
                 file_content = f.read()
                 return file_content.count(FILE_NAME)
 
diff --git a/test/functional/feature_taproot.py b/test/functional/feature_taproot.py
index 24cb26a3440..d3c1ac03791 100755
--- a/test/functional/feature_taproot.py
+++ b/test/functional/feature_taproot.py
@@ -1396,7 +1396,7 @@ def dump_json_test(tx, input_utxos, idx, success, failure):
     sha1 = hashlib.sha1(dump.encode("utf-8")).hexdigest()
     dirname = os.environ.get("TEST_DUMP_DIR", ".") + ("/%s" % sha1[0])
     os.makedirs(dirname, exist_ok=True)
-    with open(dirname + ("/%s" % sha1), 'w', encoding="utf8") as f:
+    with open(dirname + ("/%s" % sha1), 'w') as f:
         f.write(dump)
 
 # Data type to keep track of UTXOs, where they were created, and how to spend them.
diff --git a/test/functional/feature_versionbits_warning.py b/test/functional/feature_versionbits_warning.py
index 96ec7c570fa..bc4b67915b7 100755
--- a/test/functional/feature_versionbits_warning.py
+++ b/test/functional/feature_versionbits_warning.py
@@ -32,7 +32,7 @@ class VersionBitsWarningTest(BitcoinTestFramework):
     def setup_network(self):
         self.alert_filename = os.path.join(self.options.tmpdir, "alert.txt")
         # Open and close to create zero-length file
-        with open(self.alert_filename, 'w', encoding='utf8'):
+        with open(self.alert_filename, 'w'):
             pass
         self.extra_args = [[f"-alertnotify=echo %s >> \"{self.alert_filename}\""]]
         self.setup_nodes()
@@ -55,7 +55,7 @@ class VersionBitsWarningTest(BitcoinTestFramework):
 
     def versionbits_in_alert_file(self):
         """Test that the versionbits warning has been written to the alert file."""
-        with open(self.alert_filename, 'r', encoding='utf8') as f:
+        with open(self.alert_filename, 'r') as f:
             alert_text = f.read()
         return VB_PATTERN.search(alert_text) is not None
 
diff --git a/test/functional/mining_mainnet.py b/test/functional/mining_mainnet.py
index 672191006d2..122ea481735 100755
--- a/test/functional/mining_mainnet.py
+++ b/test/functional/mining_mainnet.py
@@ -83,7 +83,7 @@ class MiningMainnetTest(BitcoinTestFramework):
         path = os.path.join(os.path.dirname(os.path.realpath(__file__)), self.options.datafile)
         prev_hash = node.getbestblockhash()
         blocks = None
-        with open(path, encoding='utf-8') as f:
+        with open(path) as f:
             blocks = json.load(f)
             n_blocks = len(blocks['timestamps'])
             assert_equal(n_blocks, 2016)
diff --git a/test/functional/mocks/invalid_signer.py b/test/functional/mocks/invalid_signer.py
index 7bfa9051acc..b9a5c2a108e 100755
--- a/test/functional/mocks/invalid_signer.py
+++ b/test/functional/mocks/invalid_signer.py
@@ -11,7 +11,7 @@ import json
 def perform_pre_checks():
     mock_result_path = os.path.join(os.getcwd(), "mock_result")
     if os.path.isfile(mock_result_path):
-        with open(mock_result_path, "r", encoding="utf8") as f:
+        with open(mock_result_path, "r") as f:
             mock_result = f.read()
         if mock_result[0]:
             sys.stdout.write(mock_result[2:])
diff --git a/test/functional/mocks/signer.py b/test/functional/mocks/signer.py
index 23d163aac33..da5d9d9f752 100755
--- a/test/functional/mocks/signer.py
+++ b/test/functional/mocks/signer.py
@@ -11,7 +11,7 @@ import json
 def perform_pre_checks():
     mock_result_path = os.path.join(os.getcwd(), "mock_result")
     if os.path.isfile(mock_result_path):
-        with open(mock_result_path, "r", encoding="utf8") as f:
+        with open(mock_result_path, "r") as f:
             mock_result = f.read()
         if mock_result[0]:
             sys.stdout.write(mock_result[2:])
@@ -60,7 +60,7 @@ def signtx(args):
     if args.fingerprint != "00000001":
         return sys.stdout.write(json.dumps({"error": "Unexpected fingerprint", "fingerprint": args.fingerprint}))
 
-    with open(os.path.join(os.getcwd(), "mock_psbt"), "r", encoding="utf8") as f:
+    with open(os.path.join(os.getcwd(), "mock_psbt"), "r") as f:
         mock_psbt = f.read()
 
     if args.fingerprint == "00000001" :
diff --git a/test/functional/rpc_createmultisig.py b/test/functional/rpc_createmultisig.py
index 1675aa0c527..5ae6c39e251 100755
--- a/test/functional/rpc_createmultisig.py
+++ b/test/functional/rpc_createmultisig.py
@@ -184,7 +184,7 @@ class RpcCreateMultiSigTest(BitcoinTestFramework):
 
     def test_sortedmulti_descriptors_bip67(self):
         self.log.info('Testing sortedmulti descriptors with BIP 67 test vectors')
-        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_bip67.json'), encoding='utf-8') as f:
+        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_bip67.json')) as f:
             vectors = json.load(f)
 
         for t in vectors:
diff --git a/test/functional/rpc_decodescript.py b/test/functional/rpc_decodescript.py
index 4f127fa8b7f..40a53ce24de 100755
--- a/test/functional/rpc_decodescript.py
+++ b/test/functional/rpc_decodescript.py
@@ -266,7 +266,7 @@ class DecodeScriptTest(BitcoinTestFramework):
         assert_equal('OP_RETURN 3011020701010101010101020601010101010101', rpc_result['vin'][0]['scriptSig']['asm'])
 
     def decodescript_datadriven_tests(self):
-        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_decodescript.json'), encoding='utf-8') as f:
+        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_decodescript.json')) as f:
             dd_tests = json.load(f)
 
         for script, result in dd_tests:
diff --git a/test/functional/rpc_getblockstats.py b/test/functional/rpc_getblockstats.py
index 7def4f8fa50..fee23d20b93 100755
--- a/test/functional/rpc_getblockstats.py
+++ b/test/functional/rpc_getblockstats.py
@@ -78,11 +78,11 @@ class GetblockstatsTest(BitcoinTestFramework):
             'mocktime': int(mocktime),
             'stats': self.expected_stats,
         }
-        with open(filename, 'w', encoding="utf8") as f:
+        with open(filename, 'w') as f:
             json.dump(to_dump, f, sort_keys=True, indent=2)
 
     def load_test_data(self, filename):
-        with open(filename, 'r', encoding="utf8") as f:
+        with open(filename, 'r') as f:
             d = json.load(f)
             blocks = d['blocks']
             mocktime = d['mocktime']
diff --git a/test/functional/rpc_help.py b/test/functional/rpc_help.py
index 74d34ddca1a..92ee5d15966 100755
--- a/test/functional/rpc_help.py
+++ b/test/functional/rpc_help.py
@@ -22,7 +22,7 @@ def process_mapping(fname):
     cmds = []
     string_params = []
     in_rpcs = False
-    with open(fname, "r", encoding="utf8") as f:
+    with open(fname, "r") as f:
         for line in f:
             line = line.rstrip()
             if not in_rpcs:
@@ -153,7 +153,7 @@ class HelpRpcTest(BitcoinTestFramework):
         os.mkdir(dump_dir)
         calls = [line.split(' ', 1)[0] for line in self.nodes[0].help().splitlines() if line and not line.startswith('==')]
         for call in calls:
-            with open(os.path.join(dump_dir, call), 'w', encoding='utf-8') as f:
+            with open(os.path.join(dump_dir, call), 'w') as f:
                 # Make sure the node can generate the help at runtime without crashing
                 f.write(self.nodes[0].help(call))
 
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index 3943abcec40..1cd2a1da772 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -799,7 +799,7 @@ class PSBTTest(BitcoinTestFramework):
         assert_equal(unknown_psbt, unknown_out)
 
         # Open the data file
-        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_psbt.json'), encoding='utf-8') as f:
+        with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_psbt.json')) as f:
             d = json.load(f)
             invalids = d['invalid']
             invalid_with_msgs = d["invalid_with_msg"]
diff --git a/test/functional/rpc_signer.py b/test/functional/rpc_signer.py
index 715520b1507..0cfc2324429 100755
--- a/test/functional/rpc_signer.py
+++ b/test/functional/rpc_signer.py
@@ -37,7 +37,7 @@ class RPCSignerTest(BitcoinTestFramework):
         self.skip_if_no_external_signer()
 
     def set_mock_result(self, node, res):
-        with open(os.path.join(node.cwd, "mock_result"), "w", encoding="utf8") as f:
+        with open(os.path.join(node.cwd, "mock_result"), "w") as f:
             f.write(res)
 
     def clear_mock_result(self, node):
diff --git a/test/functional/rpc_users.py b/test/functional/rpc_users.py
index 9e475bbe853..a12adc80e34 100755
--- a/test/functional/rpc_users.py
+++ b/test/functional/rpc_users.py
@@ -61,11 +61,11 @@ class HTTPBasicsTest(BitcoinTestFramework):
         rpcauth3 = lines[1]
         self.password = lines[3]
 
-        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a") as f:
             f.write(rpcauth + "\n")
             f.write(rpcauth2 + "\n")
             f.write(rpcauth3 + "\n")
-        with open(self.nodes[1].datadir_path / "bitcoin.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[1].datadir_path / "bitcoin.conf", "a") as f:
             f.write("rpcuser={}\n".format(self.rpcuser))
             f.write("rpcpassword={}\n".format(self.rpcpassword))
         self.restart_node(0)
diff --git a/test/functional/rpc_whitelist.py b/test/functional/rpc_whitelist.py
index b103289fab3..5acae0cbcbc 100755
--- a/test/functional/rpc_whitelist.py
+++ b/test/functional/rpc_whitelist.py
@@ -61,7 +61,7 @@ class RPCWhitelistTest(BitcoinTestFramework):
         ]
         # These commands shouldn't be allowed for any user to test failures
         self.never_allowed = ["getnetworkinfo"]
-        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a", encoding="utf8") as f:
+        with open(self.nodes[0].datadir_path / "bitcoin.conf", "a") as f:
             f.write("\nrpcwhitelistdefault=0\n")
             for user in self.users:
                 f.write("rpcauth=" + user[0] + ":" + user[1] + "\n")
@@ -96,7 +96,7 @@ class RPCWhitelistTest(BitcoinTestFramework):
 
         # Replace file configurations
         self.nodes[0].replace_in_config([("rpcwhitelistdefault=0", "rpcwhitelistdefault=1")])
-        with open(self.nodes[0].datadir_path / "bitcoin.conf", 'a', encoding='utf8') as f:
+        with open(self.nodes[0].datadir_path / "bitcoin.conf", 'a') as f:
             f.write("rpcwhitelist=__cookie__:getblockcount,getblockchaininfo,getmempoolinfo,stop\n")
         self.restart_node(0)
 
diff --git a/test/functional/test_framework/coverage.py b/test/functional/test_framework/coverage.py
index 912a945d958..29e918d426d 100644
--- a/test/functional/test_framework/coverage.py
+++ b/test/functional/test_framework/coverage.py
@@ -55,7 +55,7 @@ class AuthServiceProxyWrapper():
         rpc_method = self.auth_service_proxy_instance._service_name
 
         if self.coverage_logfile:
-            with open(self.coverage_logfile, 'a+', encoding='utf8') as f:
+            with open(self.coverage_logfile, 'a+') as f:
                 f.write("%s\n" % rpc_method)
 
     def __truediv__(self, relative_uri):
@@ -107,7 +107,7 @@ def write_all_rpc_commands(dirname: str, node: AuthServiceProxy) -> bool:
         if line and not line.startswith('='):
             commands.add("%s\n" % line.split()[0])
 
-    with open(filename, 'w', encoding='utf8') as f:
+    with open(filename, 'w') as f:
         f.writelines(list(commands))
 
     return True
diff --git a/test/functional/test_framework/crypto/ellswift.py b/test/functional/test_framework/crypto/ellswift.py
index 429b7b9f4d3..4880ef5b3b6 100644
--- a/test/functional/test_framework/crypto/ellswift.py
+++ b/test/functional/test_framework/crypto/ellswift.py
@@ -134,7 +134,7 @@ class TestFrameworkEllSwift(unittest.TestCase):
     def test_elligator_encode_testvectors(self):
         """Implement the BIP324 test vectors for ellswift encoding (read from xswiftec_inv_test_vectors.csv)."""
         vectors_file = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'xswiftec_inv_test_vectors.csv')
-        with open(vectors_file, newline='', encoding='utf8') as csvfile:
+        with open(vectors_file, newline='') as csvfile:
             reader = csv.DictReader(csvfile)
             for row in reader:
                 u = FE.from_bytes(bytes.fromhex(row['u']))
@@ -150,7 +150,7 @@ class TestFrameworkEllSwift(unittest.TestCase):
     def test_elligator_decode_testvectors(self):
         """Implement the BIP324 test vectors for ellswift decoding (read from ellswift_decode_test_vectors.csv)."""
         vectors_file = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'ellswift_decode_test_vectors.csv')
-        with open(vectors_file, newline='', encoding='utf8') as csvfile:
+        with open(vectors_file, newline='') as csvfile:
             reader = csv.DictReader(csvfile)
             for row in reader:
                 encoding = bytes.fromhex(row['ellswift'])
diff --git a/test/functional/test_framework/key.py b/test/functional/test_framework/key.py
index 558dcbf23ed..6caafe8bcdb 100644
--- a/test/functional/test_framework/key.py
+++ b/test/functional/test_framework/key.py
@@ -316,7 +316,7 @@ class TestFrameworkKey(unittest.TestCase):
         """Implement the BIP340 test vectors (read from bip340_test_vectors.csv)."""
         num_tests = 0
         vectors_file = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'bip340_test_vectors.csv')
-        with open(vectors_file, newline='', encoding='utf8') as csvfile:
+        with open(vectors_file, newline='') as csvfile:
             reader = csv.reader(csvfile)
             next(reader)
             for row in reader:
diff --git a/test/functional/test_framework/netutil.py b/test/functional/test_framework/netutil.py
index f79a8c361a8..6cb34eb8156 100644
--- a/test/functional/test_framework/netutil.py
+++ b/test/functional/test_framework/netutil.py
@@ -69,7 +69,7 @@ def netstat(typ='tcp'):
     To get pid of all network process running on system, you must run this script
     as superuser
     '''
-    with open('/proc/net/'+typ,'r',encoding='utf8') as f:
+    with open('/proc/net/'+typ,'r') as f:
         content = f.readlines()
         content.pop(0)
     result = []
diff --git a/test/functional/test_framework/test_framework.py b/test/functional/test_framework/test_framework.py
index 503120213a6..a74ab5aed92 100755
--- a/test/functional/test_framework/test_framework.py
+++ b/test/functional/test_framework/test_framework.py
@@ -751,7 +751,7 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         self.log = logging.getLogger('TestFramework')
         self.log.setLevel(logging.DEBUG)
         # Create file handler to log all messages
-        fh = logging.FileHandler(self.options.tmpdir + '/test_framework.log', encoding='utf-8')
+        fh = logging.FileHandler(self.options.tmpdir + '/test_framework.log')
         fh.setLevel(logging.DEBUG)
         # Create console handler to log messages to stderr. By default this logs only error messages, but can be configured with --loglevel.
         ch = logging.StreamHandler(sys.stdout)
diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
index 4186cec5b75..060a932d1c8 100755
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -506,13 +506,13 @@ class TestNode():
         The substitutions are passed as a list of search-replace-tuples, e.g.
             [("old", "new"), ("foo", "bar"), ...]
         """
-        with open(self.bitcoinconf, 'r', encoding='utf8') as conf:
+        with open(self.bitcoinconf, 'r') as conf:
             conf_data = conf.read()
         for replacement in replacements:
             assert_equal(len(replacement), 2)
             old, new = replacement[0], replacement[1]
             conf_data = conf_data.replace(old, new)
-        with open(self.bitcoinconf, 'w', encoding='utf8') as conf:
+        with open(self.bitcoinconf, 'w') as conf:
             conf.write(conf_data)
 
     @property
diff --git a/test/functional/test_framework/util.py b/test/functional/test_framework/util.py
index bbad6ea7710..f08b36d5e9a 100644
--- a/test/functional/test_framework/util.py
+++ b/test/functional/test_framework/util.py
@@ -528,7 +528,7 @@ def write_config(config_path, *, n, chain, extra_config="", disable_autoconnect=
     else:
         chain_name_conf_arg = chain
         chain_name_conf_section = chain
-    with open(config_path, 'w', encoding='utf8') as f:
+    with open(config_path, 'w') as f:
         if chain_name_conf_arg:
             f.write("{}=1\n".format(chain_name_conf_arg))
         if chain_name_conf_section:
@@ -594,7 +594,7 @@ def get_temp_default_datadir(temp_dir: pathlib.Path) -> tuple[dict, pathlib.Path
 
 
 def append_config(datadir, options):
-    with open(os.path.join(datadir, "bitcoin.conf"), 'a', encoding='utf8') as f:
+    with open(os.path.join(datadir, "bitcoin.conf"), 'a') as f:
         for option in options:
             f.write(option + "\n")
 
@@ -603,7 +603,7 @@ def get_auth_cookie(datadir, chain):
     user = None
     password = None
     if os.path.isfile(os.path.join(datadir, "bitcoin.conf")):
-        with open(os.path.join(datadir, "bitcoin.conf"), 'r', encoding='utf8') as f:
+        with open(os.path.join(datadir, "bitcoin.conf"), 'r') as f:
             for line in f:
                 if line.startswith("rpcuser="):
                     assert user is None  # Ensure that there is only one rpcuser line
@@ -612,7 +612,7 @@ def get_auth_cookie(datadir, chain):
                     assert password is None  # Ensure that there is only one rpcpassword line
                     password = line.split("=")[1].strip("\n")
     try:
-        with open(os.path.join(datadir, chain, ".cookie"), 'r', encoding="ascii") as f:
+        with open(os.path.join(datadir, chain, ".cookie"), 'r') as f:
             userpass = f.read()
             split_userpass = userpass.split(':')
             user = split_userpass[0]
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 8c26ab952ac..d63dbadefd3 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -428,7 +428,7 @@ def main():
     # Read config generated by configure.
     config = configparser.ConfigParser()
     configfile = os.path.abspath(os.path.dirname(__file__)) + "/../config.ini"
-    config.read_file(open(configfile, encoding="utf8"))
+    config.read_file(open(configfile))
 
     passon_args.append("--configfile=%s" % configfile)
 
@@ -699,7 +699,7 @@ def print_results(test_results, max_len_name, runtime):
 
 
 def write_results(test_results, filepath, total_runtime):
-    with open(filepath, mode="w", encoding="utf8") as results_file:
+    with open(filepath, mode="w") as results_file:
         results_writer = csv.writer(results_file)
         results_writer.writerow(['test', 'status', 'duration(seconds)'])
         all_passed = True
@@ -911,7 +911,7 @@ class RPCCoverage():
         if not os.path.isfile(coverage_ref_filename):
             raise RuntimeError("No coverage reference found")
 
-        with open(coverage_ref_filename, 'r', encoding="utf8") as coverage_ref_file:
+        with open(coverage_ref_filename, 'r') as coverage_ref_file:
             all_cmds.update([line.strip() for line in coverage_ref_file.readlines()])
 
         for root, _, files in os.walk(self.dir):
@@ -920,7 +920,7 @@ class RPCCoverage():
                     coverage_filenames.add(os.path.join(root, filename))
 
         for filename in coverage_filenames:
-            with open(filename, 'r', encoding="utf8") as coverage_file:
+            with open(filename, 'r') as coverage_file:
                 covered_cmds.update([line.strip() for line in coverage_file.readlines()])
 
         return all_cmds - covered_cmds
diff --git a/test/functional/tool_utils.py b/test/functional/tool_utils.py
index 6dfe27c3466..525285deb0c 100755
--- a/test/functional/tool_utils.py
+++ b/test/functional/tool_utils.py
@@ -28,7 +28,7 @@ class ToolUtils(BitcoinTestFramework):
     def run_test(self):
         self.testcase_dir = Path(self.config["environment"]["SRCDIR"]) / "test" / "functional" / "data" / "util"
         self.bins = self.get_binaries()
-        with open(self.testcase_dir / "bitcoin-util-test.json", encoding="utf8") as f:
+        with open(self.testcase_dir / "bitcoin-util-test.json") as f:
             input_data = json.loads(f.read())
 
         for i, test_obj in enumerate(input_data):
@@ -50,7 +50,7 @@ class ToolUtils(BitcoinTestFramework):
         # Read the input data (if there is any)
         inputData = None
         if "input" in testObj:
-            with open(self.testcase_dir / testObj["input"], encoding="utf8") as f:
+            with open(self.testcase_dir / testObj["input"]) as f:
                 inputData = f.read()
 
         # Read the expected output data (if there is any)
@@ -60,7 +60,7 @@ class ToolUtils(BitcoinTestFramework):
         if "output_cmp" in testObj:
             outputFn = testObj['output_cmp']
             outputType = os.path.splitext(outputFn)[1][1:]  # output type from file extension (determines how to compare)
-            with open(self.testcase_dir / outputFn, encoding="utf8") as f:
+            with open(self.testcase_dir / outputFn) as f:
                 outputData = f.read()
             if not outputData:
                 raise Exception(f"Output data missing for {outputFn}")
diff --git a/test/functional/tool_wallet.py b/test/functional/tool_wallet.py
index bbf84d7a017..d5bc4ad67b4 100755
--- a/test/functional/tool_wallet.py
+++ b/test/functional/tool_wallet.py
@@ -83,7 +83,7 @@ class ToolWalletTest(BitcoinTestFramework):
 
     def read_dump(self, filename):
         dump = OrderedDict()
-        with open(filename, "r", encoding="utf8") as f:
+        with open(filename, "r") as f:
             for row in f:
                 row = row.strip()
                 key, value = row.split(',')
@@ -98,7 +98,7 @@ class ToolWalletTest(BitcoinTestFramework):
     def write_dump(self, dump, filename, magic=None, skip_checksum=False):
         if magic is None:
             magic = "BITCOIN_CORE_WALLET_DUMP"
-        with open(filename, "w", encoding="utf8") as f:
+        with open(filename, "w") as f:
             row = ",".join([magic, dump[magic]]) + "\n"
             f.write(row)
             for k, v in dump.items():
diff --git a/test/functional/wallet_backup.py b/test/functional/wallet_backup.py
index 6f3637a0dda..4d08ace424c 100755
--- a/test/functional/wallet_backup.py
+++ b/test/functional/wallet_backup.py
@@ -112,7 +112,7 @@ class WalletBackupTest(BitcoinTestFramework):
     def restore_invalid_wallet(self):
         node = self.nodes[3]
         invalid_wallet_file = self.nodes[0].datadir_path / 'invalid_wallet_file.bak'
-        open(invalid_wallet_file, 'a', encoding="utf8").write('invald wallet')
+        open(invalid_wallet_file, 'a').write('invald wallet')
         wallet_name = "res0"
         not_created_wallet_file = node.wallets_path / wallet_name
         error_message = "Wallet file verification failed. Failed to load database path '{}'. Data is not in recognized format.".format(not_created_wallet_file)
diff --git a/test/functional/wallet_backwards_compatibility.py b/test/functional/wallet_backwards_compatibility.py
index 1f335398738..a67b4676a86 100755
--- a/test/functional/wallet_backwards_compatibility.py
+++ b/test/functional/wallet_backwards_compatibility.py
@@ -100,7 +100,7 @@ class BackwardsCompatibilityTest(BitcoinTestFramework):
         bad_deriv_wallet.dumpwallet(dump_path)
         addr = None
         seed = None
-        with open(dump_path, encoding="utf8") as f:
+        with open(dump_path) as f:
             for line in f:
                 if f"hdkeypath=m/0'/0'/{LAST_KEYPOOL_INDEX}'" in line:
                     addr = line.split(" ")[4].split("=")[1]
@@ -123,7 +123,7 @@ class BackwardsCompatibilityTest(BitcoinTestFramework):
         os.unlink(dump_path)
         bad_deriv_wallet.dumpwallet(dump_path)
         bad_path_addr = None
-        with open(dump_path, encoding="utf8") as f:
+        with open(dump_path) as f:
             for line in f:
                 if f"hdkeypath={bad_deriv_path}" in line:
                     bad_path_addr = line.split(" ")[4].split("=")[1]
diff --git a/test/functional/wallet_encryption.py b/test/functional/wallet_encryption.py
index b54852b7c33..f8182e10c18 100755
--- a/test/functional/wallet_encryption.py
+++ b/test/functional/wallet_encryption.py
@@ -134,13 +134,13 @@ class WalletEncryptionTest(BitcoinTestFramework):
             do_wallet_tool("-wallet=noprivs", f"-dumpfile={dumpfile_path}", "dump")
 
             # Modify the dump
-            with open(dumpfile_path, "r", encoding="utf-8") as f:
+            with open(dumpfile_path, "r") as f:
                 dump_content = f.readlines()
             # Drop the checksum line
             dump_content = dump_content[:-1]
             # Insert a valid mkey line. This corresponds to a passphrase of "pass".
             dump_content.append("046d6b657901000000,300dc926f3b3887aad3d5d5f5a0fc1b1a4a1722f9284bd5c6ff93b64a83902765953939c58fe144013c8b819f42cf698b208e9911e5f0c544fa300000000cc52050000\n")
-            with open(dumpfile_path, "w", encoding="utf-8") as f:
+            with open(dumpfile_path, "w") as f:
                 contents = "".join(dump_content)
                 f.write(contents)
                 checksum = hash256(contents.encode())
@@ -158,7 +158,7 @@ class WalletEncryptionTest(BitcoinTestFramework):
             # Make a new dump and check that there are no mkeys
             dumpfile_path = self.nodes[0].datadir_path / "noprivs_enc.dump"
             do_wallet_tool("-wallet=noprivs_enc", f"-dumpfile={dumpfile_path}", "dump")
-            with open(dumpfile_path, "r", encoding="utf-8") as f:
+            with open(dumpfile_path, "r") as f:
                 # Check there's nothing with an 'mkey' prefix
                 assert_equal(all([not line.startswith("046d6b6579") for line in f]), True)
 
diff --git a/test/functional/wallet_multiwallet.py b/test/functional/wallet_multiwallet.py
index 64f57cecf66..f15c1506875 100755
--- a/test/functional/wallet_multiwallet.py
+++ b/test/functional/wallet_multiwallet.py
@@ -180,7 +180,7 @@ class MultiWalletTest(BitcoinTestFramework):
         self.nodes[0].assert_start_raises_init_error(['-walletdir=bad'], 'Error: Specified -walletdir "bad" does not exist')
         # should not initialize if the specified walletdir is not a directory
         not_a_dir = wallet_dir('notadir')
-        open(not_a_dir, 'a', encoding="utf8").close()
+        open(not_a_dir, 'a').close()
         self.nodes[0].assert_start_raises_init_error(['-walletdir=' + not_a_dir], 'Error: Specified -walletdir "' + not_a_dir + '" is not a directory')
 
         # if wallets/ doesn't exist, datadir should be the default wallet dir
diff --git a/test/functional/wallet_signer.py b/test/functional/wallet_signer.py
index c239bb61694..52780e6fb88 100755
--- a/test/functional/wallet_signer.py
+++ b/test/functional/wallet_signer.py
@@ -48,7 +48,7 @@ class WalletSignerTest(BitcoinTestFramework):
         self.skip_if_no_wallet()
 
     def set_mock_result(self, node, res):
-        with open(os.path.join(node.cwd, "mock_result"), "w", encoding="utf8") as f:
+        with open(os.path.join(node.cwd, "mock_result"), "w") as f:
             f.write(res)
 
     def clear_mock_result(self, node):
@@ -170,7 +170,7 @@ class WalletSignerTest(BitcoinTestFramework):
 
         assert hww.testmempoolaccept([mock_tx])[0]["allowed"]
 
-        with open(os.path.join(self.nodes[1].cwd, "mock_psbt"), "w", encoding="utf8") as f:
+        with open(os.path.join(self.nodes[1].cwd, "mock_psbt"), "w") as f:
             f.write(mock_psbt_signed["psbt"])
 
         self.log.info('Test send using hww1')
@@ -195,7 +195,7 @@ class WalletSignerTest(BitcoinTestFramework):
         mock_psbt_bumped = mock_wallet.psbtbumpfee(orig_tx_id)["psbt"]
         mock_psbt_bumped_signed = mock_wallet.walletprocesspsbt(psbt=mock_psbt_bumped, sign=True, sighashtype="ALL", bip32derivs=True)
 
-        with open(os.path.join(self.nodes[1].cwd, "mock_psbt"), "w", encoding="utf8") as f:
+        with open(os.path.join(self.nodes[1].cwd, "mock_psbt"), "w") as f:
             f.write(mock_psbt_bumped_signed["psbt"])
 
         self.log.info('Test bumpfee using hww1')
diff --git a/test/fuzz/test_runner.py b/test/fuzz/test_runner.py
index 5b2c847bbbb..d31d95edfba 100755
--- a/test/fuzz/test_runner.py
+++ b/test/fuzz/test_runner.py
@@ -99,7 +99,7 @@ def main():
     # Read config generated by configure.
     config = configparser.ConfigParser()
     configfile = os.path.abspath(os.path.dirname(__file__)) + "/../config.ini"
-    config.read_file(open(configfile, encoding="utf8"))
+    config.read_file(open(configfile))
 
     if not config["components"].getboolean("ENABLE_FUZZ_BINARY"):
         logging.error("Must have fuzz executable built")
diff --git a/test/lint/lint-files.py b/test/lint/lint-files.py
index c5af959e0a8..cddaed98db3 100755
--- a/test/lint/lint-files.py
+++ b/test/lint/lint-files.py
@@ -185,7 +185,7 @@ def check_shebang_file_permissions(files_meta) -> int:
 
             # *.py files which don't contain an `if __name__ == '__main__'` are not expected to be executed directly
             if file_meta.extension == "py":
-                with open(filename, "r", encoding="utf8") as f:
+                with open(filename, "r") as f:
                     file_data = f.read()
                 if not re.search("""if __name__ == ['"]__main__['"]:""", file_data):
                     continue
diff --git a/test/lint/lint-include-guards.py b/test/lint/lint-include-guards.py
index e16bb94a770..e0d4eb95fd5 100755
--- a/test/lint/lint-include-guards.py
+++ b/test/lint/lint-include-guards.py
@@ -71,7 +71,7 @@ def main():
 
         regex_pattern = f'^#(ifndef|define|endif //) {header_id}'
 
-        with open(header_file, 'r', encoding='utf-8') as f:
+        with open(header_file, 'r') as f:
             header_file_contents = f.readlines()
 
         count = 0
diff --git a/test/lint/lint-includes.py b/test/lint/lint-includes.py
index b0c91b90114..0f108904b84 100755
--- a/test/lint/lint-includes.py
+++ b/test/lint/lint-includes.py
@@ -40,13 +40,13 @@ EXPECTED_BOOST_INCLUDES = [
 
 
 def get_toplevel():
-    return check_output(["git", "rev-parse", "--show-toplevel"], text=True, encoding="utf8").rstrip("\n")
+    return check_output(["git", "rev-parse", "--show-toplevel"], text=True).rstrip("\n")
 
 
 def list_files_by_suffix(suffixes):
     exclude_args = [":(exclude)" + dir for dir in EXCLUDED_DIRS]
 
-    files_list = check_output(["git", "ls-files", "src"] + exclude_args, text=True, encoding="utf8").splitlines()
+    files_list = check_output(["git", "ls-files", "src"] + exclude_args, text=True).splitlines()
 
     return [file for file in files_list if file.endswith(suffixes)]
 
@@ -68,7 +68,7 @@ def find_included_cpps():
     included_cpps = list()
 
     try:
-        included_cpps = check_output(["git", "grep", "-E", r"^#include [<\"][^>\"]+\.cpp[>\"]", "--", "*.cpp", "*.h"], text=True, encoding="utf8").splitlines()
+        included_cpps = check_output(["git", "grep", "-E", r"^#include [<\"][^>\"]+\.cpp[>\"]", "--", "*.cpp", "*.h"], text=True).splitlines()
     except CalledProcessError as e:
         if e.returncode > 1:
             raise e
@@ -82,7 +82,7 @@ def find_extra_boosts():
     exclusion_set = set()
 
     try:
-        included_boosts = check_output(["git", "grep", "-E", r"^#include <boost/", "--", "*.cpp", "*.h"], text=True, encoding="utf8").splitlines()
+        included_boosts = check_output(["git", "grep", "-E", r"^#include <boost/", "--", "*.cpp", "*.h"], text=True).splitlines()
     except CalledProcessError as e:
         if e.returncode > 1:
             raise e
@@ -105,7 +105,7 @@ def find_quote_syntax_inclusions():
     quote_syntax_inclusions = list()
 
     try:
-        quote_syntax_inclusions = check_output(["git", "grep", r"^#include \"", "--", "*.cpp", "*.h"] + exclude_args, text=True, encoding="utf8").splitlines()
+        quote_syntax_inclusions = check_output(["git", "grep", r"^#include \"", "--", "*.cpp", "*.h"] + exclude_args, text=True).splitlines()
     except CalledProcessError as e:
         if e.returncode > 1:
             raise e
@@ -120,7 +120,7 @@ def main():
 
     # Check for duplicate includes
     for filename in list_files_by_suffix((".cpp", ".h")):
-        with open(filename, "r", encoding="utf8") as file:
+        with open(filename, "r") as file:
             include_list = [line.rstrip("\n") for line in file if re.match(r"^#include", line)]
 
         duplicates = find_duplicate_includes(include_list)
@@ -148,13 +148,13 @@ def main():
     if extra_boosts:
         for boost in extra_boosts:
             print(f"A new Boost dependency in the form of \"{boost}\" appears to have been introduced:")
-            print(check_output(["git", "grep", boost, "--", "*.cpp", "*.h"], text=True, encoding="utf8"))
+            print(check_output(["git", "grep", boost, "--", "*.cpp", "*.h"], text=True))
         exit_code = 1
 
     # Check if Boost dependencies are no longer used
     for expected_boost in EXPECTED_BOOST_INCLUDES:
         try:
-            check_output(["git", "grep", "-q", r"^#include <%s>" % expected_boost, "--", "*.cpp", "*.h"], text=True, encoding="utf8")
+            check_output(["git", "grep", "-q", r"^#include <%s>" % expected_boost, "--", "*.cpp", "*.h"], text=True)
         except CalledProcessError as e:
             if e.returncode > 1:
                 raise e
diff --git a/test/lint/lint-locale-dependence.py b/test/lint/lint-locale-dependence.py
index e728123e694..c6a64587091 100755
--- a/test/lint/lint-locale-dependence.py
+++ b/test/lint/lint-locale-dependence.py
@@ -219,7 +219,7 @@ def find_locale_dependent_function_uses():
     git_grep_output = list()
 
     try:
-        git_grep_output = check_output(git_grep_command, text=True, encoding="utf8").splitlines()
+        git_grep_output = check_output(git_grep_command, text=True).splitlines()
     except CalledProcessError as e:
         if e.returncode > 1:
             raise e
diff --git a/test/lint/lint-shell-locale.py b/test/lint/lint-shell-locale.py
index 59515e7888d..3602289d18a 100755
--- a/test/lint/lint-shell-locale.py
+++ b/test/lint/lint-shell-locale.py
@@ -41,7 +41,7 @@ def main():
         if re.search('src/(secp256k1|minisketch)/', file_path):
             continue
 
-        with open(file_path, 'r', encoding='utf-8') as file_obj:
+        with open(file_path, 'r') as file_obj:
             contents = file_obj.read()
 
         non_comment_pattern = re.compile(r'^\s*((?!#).+)$', re.MULTILINE)
diff --git a/test/lint/lint-tests.py b/test/lint/lint-tests.py
index 100339d217b..f4072d691c9 100755
--- a/test/lint/lint-tests.py
+++ b/test/lint/lint-tests.py
@@ -23,7 +23,7 @@ def grep_boost_fixture_test_suite():
         "src/test/**.cpp",
         "src/wallet/test/**.cpp",
     ]
-    return subprocess.check_output(command, text=True, encoding="utf8")
+    return subprocess.check_output(command, text=True)
 
 
 def check_matching_test_names(test_suite_list):